/*
 * fsm.c - {Link, IP} Control Protocol Finite State Machine.
 *
 * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "netif/ppp/ppp_opts.h"
#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */

/*
 * @todo:
 * Randomize fsm id on link/init.
 * Deal with variable outgoing MTU.
 */

#if 0 /* UNUSED */
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#endif /* UNUSED */

#include "netif/ppp/ppp_impl.h"

#include "netif/ppp/fsm.h"

static void fsm_timeout(void *);
static void fsm_rconfreq(fsm *f, u_char id, u_char *inp, int len);
static void fsm_rconfack(fsm *f, int id, u_char *inp, int len);
static void fsm_rconfnakrej(fsm *f, int code, int id, u_char *inp, int len);
static void fsm_rtermreq(fsm *f, int id, u_char *p, int len);
static void fsm_rtermack(fsm *f);
static void fsm_rcoderej(fsm *f, u_char *inp, int len);
static void fsm_sconfreq(fsm *f, int retransmit);

#define PROTO_NAME(f) ((f)->callbacks->proto_name)

/*
 * fsm_init - Initialize fsm.
 *
 * Initialize fsm state.
 */
void fsm_init(fsm *f) {
  ppp_pcb *pcb = f->pcb;
  f->state = PPP_FSM_INITIAL;
  f->flags = 0;
  f->id = 0; /* XXX Start with random id? */
  f->maxnakloops = pcb->settings.fsm_max_nak_loops;
  f->term_reason_len = 0;
}

/*
 * fsm_lowerup - The lower layer is up.
 */
void fsm_lowerup(fsm *f) {
  switch (f->state) {
  case PPP_FSM_INITIAL:
    f->state = PPP_FSM_CLOSED;
    break;

  case PPP_FSM_STARTING:
    if (f->flags & OPT_SILENT)
      f->state = PPP_FSM_STOPPED;
    else {
      /* Send an initial configure-request */
      fsm_sconfreq(f, 0);
      f->state = PPP_FSM_REQSENT;
    }
    break;

  default:
    FSMDEBUG(("%s: Up event in state %d!", PROTO_NAME(f), f->state));
    /* no break */
  }
}

/*
 * fsm_lowerdown - The lower layer is down.
 *
 * Cancel all timeouts and inform upper layers.
 */
void fsm_lowerdown(fsm *f) {
  switch (f->state) {
  case PPP_FSM_CLOSED:
    f->state = PPP_FSM_INITIAL;
    break;

  case PPP_FSM_STOPPED:
    f->state = PPP_FSM_STARTING;
    if (f->callbacks->starting)
      (*f->callbacks->starting)(f);
    break;

  case PPP_FSM_CLOSING:
    f->state = PPP_FSM_INITIAL;
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
    break;

  case PPP_FSM_STOPPING:
  case PPP_FSM_REQSENT:
  case PPP_FSM_ACKRCVD:
  case PPP_FSM_ACKSENT:
    f->state = PPP_FSM_STARTING;
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
    break;

  case PPP_FSM_OPENED:
    if (f->callbacks->down)
      (*f->callbacks->down)(f);
    f->state = PPP_FSM_STARTING;
    break;

  default:
    FSMDEBUG(("%s: Down event in state %d!", PROTO_NAME(f), f->state));
    /* no break */
  }
}

/*
 * fsm_open - Link is allowed to come up.
 */
void fsm_open(fsm *f) {
  switch (f->state) {
  case PPP_FSM_INITIAL:
    f->state = PPP_FSM_STARTING;
    if (f->callbacks->starting)
      (*f->callbacks->starting)(f);
    break;

  case PPP_FSM_CLOSED:
    if (f->flags & OPT_SILENT)
      f->state = PPP_FSM_STOPPED;
    else {
      /* Send an initial configure-request */
      fsm_sconfreq(f, 0);
      f->state = PPP_FSM_REQSENT;
    }
    break;

  case PPP_FSM_CLOSING:
    f->state = PPP_FSM_STOPPING;
    /* fall through */
    /* no break */
  case PPP_FSM_STOPPED:
  case PPP_FSM_OPENED:
    if (f->flags & OPT_RESTART) {
      fsm_lowerdown(f);
      fsm_lowerup(f);
    }
    break;
  default:
    break;
  }
}

/*
 * terminate_layer - Start process of shutting down the FSM
 *
 * Cancel any timeout running, notify upper layers we're done, and
 * send a terminate-request message as configured.
 */
static void terminate_layer(fsm *f, int nextstate) {
  ppp_pcb *pcb = f->pcb;

  if (f->state != PPP_FSM_OPENED)
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
  else if (f->callbacks->down)
    (*f->callbacks->down)(f); /* Inform upper layers we're down */

  /* Init restart counter and send Terminate-Request */
  f->retransmits = pcb->settings.fsm_max_term_transmits;
  fsm_sdata(f, TERMREQ, f->reqid = ++f->id, (const u_char *)f->term_reason,
            f->term_reason_len);

  if (f->retransmits == 0) {
    /*
     * User asked for no terminate requests at all; just close it.
     * We've already fired off one Terminate-Request just to be nice
     * to the peer, but we're not going to wait for a reply.
     */
    f->state = nextstate == PPP_FSM_CLOSING ? PPP_FSM_CLOSED : PPP_FSM_STOPPED;
    if (f->callbacks->finished)
      (*f->callbacks->finished)(f);
    return;
  }

  TIMEOUT(fsm_timeout, f, pcb->settings.fsm_timeout_time);
  --f->retransmits;

  f->state = nextstate;
}

/*
 * fsm_close - Start closing connection.
 *
 * Cancel timeouts and either initiate close or possibly go directly to
 * the PPP_FSM_CLOSED state.
 */
void fsm_close(fsm *f, const char *reason) {
  f->term_reason = reason;
  f->term_reason_len =
      (reason == NULL ? 0 : (u8_t)LWIP_MIN(strlen(reason), 0xFF));
  switch (f->state) {
  case PPP_FSM_STARTING:
    f->state = PPP_FSM_INITIAL;
    break;
  case PPP_FSM_STOPPED:
    f->state = PPP_FSM_CLOSED;
    break;
  case PPP_FSM_STOPPING:
    f->state = PPP_FSM_CLOSING;
    break;

  case PPP_FSM_REQSENT:
  case PPP_FSM_ACKRCVD:
  case PPP_FSM_ACKSENT:
  case PPP_FSM_OPENED:
    terminate_layer(f, PPP_FSM_CLOSING);
    break;
  default:
    break;
  }
}

/*
 * fsm_timeout - Timeout expired.
 */
static void fsm_timeout(void *arg) {
  fsm *f = (fsm *)arg;
  ppp_pcb *pcb = f->pcb;

  switch (f->state) {
  case PPP_FSM_CLOSING:
  case PPP_FSM_STOPPING:
    if (f->retransmits <= 0) {
      /*
       * We've waited for an ack long enough.  Peer probably heard us.
       */
      f->state =
          (f->state == PPP_FSM_CLOSING) ? PPP_FSM_CLOSED : PPP_FSM_STOPPED;
      if (f->callbacks->finished)
        (*f->callbacks->finished)(f);
    } else {
      /* Send Terminate-Request */
      fsm_sdata(f, TERMREQ, f->reqid = ++f->id, (const u_char *)f->term_reason,
                f->term_reason_len);
      TIMEOUT(fsm_timeout, f, pcb->settings.fsm_timeout_time);
      --f->retransmits;
    }
    break;

  case PPP_FSM_REQSENT:
  case PPP_FSM_ACKRCVD:
  case PPP_FSM_ACKSENT:
    if (f->retransmits <= 0) {
      ppp_warn(("%s: timeout sending Config-Requests", PROTO_NAME(f)));
      f->state = PPP_FSM_STOPPED;
      if ((f->flags & OPT_PASSIVE) == 0 && f->callbacks->finished)
        (*f->callbacks->finished)(f);

    } else {
      /* Retransmit the configure-request */
      if (f->callbacks->retransmit)
        (*f->callbacks->retransmit)(f);
      fsm_sconfreq(f, 1); /* Re-send Configure-Request */
      if (f->state == PPP_FSM_ACKRCVD)
        f->state = PPP_FSM_REQSENT;
    }
    break;

  default:
    FSMDEBUG(("%s: Timeout event in state %d!", PROTO_NAME(f), f->state));
    /* no break */
  }
}

/*
 * fsm_input - Input packet.
 */
void fsm_input(fsm *f, u_char *inpacket, int l) {
  u_char *inp;
  u_char code, id;
  int len;

  /*
   * Parse header (code, id and length).
   * If packet too short, drop it.
   */
  inp = inpacket;
  if (l < HEADERLEN) {
    FSMDEBUG(("fsm_input(%x): Rcvd short header.", f->protocol));
    return;
  }
  GETCHAR(code, inp);
  GETCHAR(id, inp);
  GETSHORT(len, inp);
  if (len < HEADERLEN) {
    FSMDEBUG(("fsm_input(%x): Rcvd illegal length.", f->protocol));
    return;
  }
  if (len > l) {
    FSMDEBUG(("fsm_input(%x): Rcvd short packet.", f->protocol));
    return;
  }
  len -= HEADERLEN; /* subtract header length */

  if (f->state == PPP_FSM_INITIAL || f->state == PPP_FSM_STARTING) {
    FSMDEBUG(
        ("fsm_input(%x): Rcvd packet in state %d.", f->protocol, f->state));
    return;
  }

  /*
   * Action depends on code.
   */
  switch (code) {
  case CONFREQ:
    fsm_rconfreq(f, id, inp, len);
    break;

  case CONFACK:
    fsm_rconfack(f, id, inp, len);
    break;

  case CONFNAK:
  case CONFREJ:
    fsm_rconfnakrej(f, code, id, inp, len);
    break;

  case TERMREQ:
    fsm_rtermreq(f, id, inp, len);
    break;

  case TERMACK:
    fsm_rtermack(f);
    break;

  case CODEREJ:
    fsm_rcoderej(f, inp, len);
    break;

  default:
    if (!f->callbacks->extcode ||
        !(*f->callbacks->extcode)(f, code, id, inp, len))
      fsm_sdata(f, CODEREJ, ++f->id, inpacket, len + HEADERLEN);
    break;
  }
}

/*
 * fsm_rconfreq - Receive Configure-Request.
 */
static void fsm_rconfreq(fsm *f, u_char id, u_char *inp, int len) {
  int code, reject_if_disagree;

  switch (f->state) {
  case PPP_FSM_CLOSED:
    /* Go away, we're closed */
    fsm_sdata(f, TERMACK, id, NULL, 0);
    return;
  case PPP_FSM_CLOSING:
  case PPP_FSM_STOPPING:
    return;

  case PPP_FSM_OPENED:
    /* Go down and restart negotiation */
    if (f->callbacks->down)
      (*f->callbacks->down)(f); /* Inform upper layers */
    fsm_sconfreq(f, 0);         /* Send initial Configure-Request */
    f->state = PPP_FSM_REQSENT;
    break;

  case PPP_FSM_STOPPED:
    /* Negotiation started by our peer */
    fsm_sconfreq(f, 0); /* Send initial Configure-Request */
    f->state = PPP_FSM_REQSENT;
    break;
  default:
    break;
  }

  /*
   * Pass the requested configuration options
   * to protocol-specific code for checking.
   */
  if (f->callbacks->reqci) { /* Check CI */
    reject_if_disagree = (f->nakloops >= f->maxnakloops);
    code = (*f->callbacks->reqci)(f, inp, &len, reject_if_disagree);
  } else if (len)
    code = CONFREJ; /* Reject all CI */
  else
    code = CONFACK;

  /* send the Ack, Nak or Rej to the peer */
  fsm_sdata(f, code, id, inp, len);

  if (code == CONFACK) {
    if (f->state == PPP_FSM_ACKRCVD) {
      UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
      f->state = PPP_FSM_OPENED;
      if (f->callbacks->up)
        (*f->callbacks->up)(f); /* Inform upper layers */
    } else
      f->state = PPP_FSM_ACKSENT;
    f->nakloops = 0;

  } else {
    /* we sent CONFACK or CONFREJ */
    if (f->state != PPP_FSM_ACKRCVD)
      f->state = PPP_FSM_REQSENT;
    if (code == CONFNAK)
      ++f->nakloops;
  }
}

/*
 * fsm_rconfack - Receive Configure-Ack.
 */
static void fsm_rconfack(fsm *f, int id, u_char *inp, int len) {
  ppp_pcb *pcb = f->pcb;

  if (id != f->reqid || f->seen_ack) /* Expected id? */
    return;                          /* Nope, toss... */
  if (!(f->callbacks->ackci ? (*f->callbacks->ackci)(f, inp, len)
                            : (len == 0))) {
    /* Ack is bad - ignore it */
    ppp_error(("Received bad configure-ack: %P", inp, len));
    return;
  }
  f->seen_ack = 1;
  f->rnakloops = 0;

  switch (f->state) {
  case PPP_FSM_CLOSED:
  case PPP_FSM_STOPPED:
    fsm_sdata(f, TERMACK, id, NULL, 0);
    break;

  case PPP_FSM_REQSENT:
    f->state = PPP_FSM_ACKRCVD;
    f->retransmits = pcb->settings.fsm_max_conf_req_transmits;
    break;

  case PPP_FSM_ACKRCVD:
    /* Huh? an extra valid Ack? oh well... */
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
    fsm_sconfreq(f, 0);
    f->state = PPP_FSM_REQSENT;
    break;

  case PPP_FSM_ACKSENT:
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
    f->state = PPP_FSM_OPENED;
    f->retransmits = pcb->settings.fsm_max_conf_req_transmits;
    if (f->callbacks->up)
      (*f->callbacks->up)(f); /* Inform upper layers */
    break;

  case PPP_FSM_OPENED:
    /* Go down and restart negotiation */
    if (f->callbacks->down)
      (*f->callbacks->down)(f); /* Inform upper layers */
    fsm_sconfreq(f, 0);         /* Send initial Configure-Request */
    f->state = PPP_FSM_REQSENT;
    break;
  default:
    break;
  }
}

/*
 * fsm_rconfnakrej - Receive Configure-Nak or Configure-Reject.
 */
static void fsm_rconfnakrej(fsm *f, int code, int id, u_char *inp, int len) {
  int ret;
  int treat_as_reject;

  if (id != f->reqid || f->seen_ack) /* Expected id? */
    return;                          /* Nope, toss... */

  if (code == CONFNAK) {
    ++f->rnakloops;
    treat_as_reject = (f->rnakloops >= f->maxnakloops);
    if (f->callbacks->nakci == NULL ||
        !(ret = f->callbacks->nakci(f, inp, len, treat_as_reject))) {
      ppp_error(("Received bad configure-nak: %P", inp, len));
      return;
    }
  } else {
    f->rnakloops = 0;
    if (f->callbacks->rejci == NULL ||
        !(ret = f->callbacks->rejci(f, inp, len))) {
      ppp_error(("Received bad configure-rej: %P", inp, len));
      return;
    }
  }

  f->seen_ack = 1;

  switch (f->state) {
  case PPP_FSM_CLOSED:
  case PPP_FSM_STOPPED:
    fsm_sdata(f, TERMACK, id, NULL, 0);
    break;

  case PPP_FSM_REQSENT:
  case PPP_FSM_ACKSENT:
    /* They didn't agree to what we wanted - try another request */
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
    if (ret < 0)
      f->state = PPP_FSM_STOPPED; /* kludge for stopping CCP */
    else
      fsm_sconfreq(f, 0); /* Send Configure-Request */
    break;

  case PPP_FSM_ACKRCVD:
    /* Got a Nak/reject when we had already had an Ack?? oh well... */
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
    fsm_sconfreq(f, 0);
    f->state = PPP_FSM_REQSENT;
    break;

  case PPP_FSM_OPENED:
    /* Go down and restart negotiation */
    if (f->callbacks->down)
      (*f->callbacks->down)(f); /* Inform upper layers */
    fsm_sconfreq(f, 0);         /* Send initial Configure-Request */
    f->state = PPP_FSM_REQSENT;
    break;
  default:
    break;
  }
}

/*
 * fsm_rtermreq - Receive Terminate-Req.
 */
static void fsm_rtermreq(fsm *f, int id, u_char *p, int len) {
  ppp_pcb *pcb = f->pcb;

  switch (f->state) {
  case PPP_FSM_ACKRCVD:
  case PPP_FSM_ACKSENT:
    f->state = PPP_FSM_REQSENT; /* Start over but keep trying */
    break;

  case PPP_FSM_OPENED:
    if (len > 0) {
      ppp_info(("%s terminated by peer (%0.*v)", PROTO_NAME(f), len, p));
    } else
      ppp_info(("%s terminated by peer", PROTO_NAME(f)));
    f->retransmits = 0;
    f->state = PPP_FSM_STOPPING;
    if (f->callbacks->down)
      (*f->callbacks->down)(f); /* Inform upper layers */
    TIMEOUT(fsm_timeout, f, pcb->settings.fsm_timeout_time);
    break;
  default:
    break;
  }

  fsm_sdata(f, TERMACK, id, NULL, 0);
}

/*
 * fsm_rtermack - Receive Terminate-Ack.
 */
static void fsm_rtermack(fsm *f) {
  switch (f->state) {
  case PPP_FSM_CLOSING:
    UNTIMEOUT(fsm_timeout, f);
    f->state = PPP_FSM_CLOSED;
    if (f->callbacks->finished)
      (*f->callbacks->finished)(f);
    break;
  case PPP_FSM_STOPPING:
    UNTIMEOUT(fsm_timeout, f);
    f->state = PPP_FSM_STOPPED;
    if (f->callbacks->finished)
      (*f->callbacks->finished)(f);
    break;

  case PPP_FSM_ACKRCVD:
    f->state = PPP_FSM_REQSENT;
    break;

  case PPP_FSM_OPENED:
    if (f->callbacks->down)
      (*f->callbacks->down)(f); /* Inform upper layers */
    fsm_sconfreq(f, 0);
    f->state = PPP_FSM_REQSENT;
    break;
  default:
    break;
  }
}

/*
 * fsm_rcoderej - Receive an Code-Reject.
 */
static void fsm_rcoderej(fsm *f, u_char *inp, int len) {
  u_char code, id;

  if (len < HEADERLEN) {
    FSMDEBUG(("fsm_rcoderej: Rcvd short Code-Reject packet!"));
    return;
  }
  GETCHAR(code, inp);
  GETCHAR(id, inp);
  ppp_warn(
      ("%s: Rcvd Code-Reject for code %d, id %d", PROTO_NAME(f), code, id));

  if (f->state == PPP_FSM_ACKRCVD)
    f->state = PPP_FSM_REQSENT;
}

/*
 * fsm_protreject - Peer doesn't speak this protocol.
 *
 * Treat this as a catastrophic error (RXJ-).
 */
void fsm_protreject(fsm *f) {
  switch (f->state) {
  case PPP_FSM_CLOSING:
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
                               /* fall through */
                               /* no break */
  case PPP_FSM_CLOSED:
    f->state = PPP_FSM_CLOSED;
    if (f->callbacks->finished)
      (*f->callbacks->finished)(f);
    break;

  case PPP_FSM_STOPPING:
  case PPP_FSM_REQSENT:
  case PPP_FSM_ACKRCVD:
  case PPP_FSM_ACKSENT:
    UNTIMEOUT(fsm_timeout, f); /* Cancel timeout */
                               /* fall through */
                               /* no break */
  case PPP_FSM_STOPPED:
    f->state = PPP_FSM_STOPPED;
    if (f->callbacks->finished)
      (*f->callbacks->finished)(f);
    break;

  case PPP_FSM_OPENED:
    terminate_layer(f, PPP_FSM_STOPPING);
    break;

  default:
    FSMDEBUG(
        ("%s: Protocol-reject event in state %d!", PROTO_NAME(f), f->state));
    /* no break */
  }
}

/*
 * fsm_sconfreq - Send a Configure-Request.
 */
static void fsm_sconfreq(fsm *f, int retransmit) {
  ppp_pcb *pcb = f->pcb;
  struct pbuf *p;
  u_char *outp;
  int cilen;

  if (f->state != PPP_FSM_REQSENT && f->state != PPP_FSM_ACKRCVD &&
      f->state != PPP_FSM_ACKSENT) {
    /* Not currently negotiating - reset options */
    if (f->callbacks->resetci)
      (*f->callbacks->resetci)(f);
    f->nakloops = 0;
    f->rnakloops = 0;
  }

  if (!retransmit) {
    /* New request - reset retransmission counter, use new ID */
    f->retransmits = pcb->settings.fsm_max_conf_req_transmits;
    f->reqid = ++f->id;
  }

  f->seen_ack = 0;

  /*
   * Make up the request packet
   */
  if (f->callbacks->cilen && f->callbacks->addci) {
    cilen = (*f->callbacks->cilen)(f);
    if (cilen > pcb->peer_mru - HEADERLEN)
      cilen = pcb->peer_mru - HEADERLEN;
  } else
    cilen = 0;

  p = pbuf_alloc(PBUF_RAW, (u16_t)(cilen + HEADERLEN + PPP_HDRLEN), PBUF_RAM);
  if (NULL == p)
    return;
  if (p->tot_len != p->len) {
    pbuf_free(p);
    return;
  }

  /* send the request to our peer */
  outp = (u_char *)p->payload;
  MAKEHEADER(outp, f->protocol);
  PUTCHAR(CONFREQ, outp);
  PUTCHAR(f->reqid, outp);
  PUTSHORT(cilen + HEADERLEN, outp);
  if (cilen != 0) {
    (*f->callbacks->addci)(f, outp, &cilen);
    LWIP_ASSERT("cilen == p->len - HEADERLEN - PPP_HDRLEN",
                cilen == p->len - HEADERLEN - PPP_HDRLEN);
  }

  ppp_write(pcb, p);

  /* start the retransmit timer */
  --f->retransmits;
  TIMEOUT(fsm_timeout, f, pcb->settings.fsm_timeout_time);
}

/*
 * fsm_sdata - Send some data.
 *
 * Used for all packets sent to our peer by this module.
 */
void fsm_sdata(fsm *f, u_char code, u_char id, const u_char *data,
               int datalen) {
  ppp_pcb *pcb = f->pcb;
  struct pbuf *p;
  u_char *outp;
  int outlen;

  /* Adjust length to be smaller than MTU */
  if (datalen > pcb->peer_mru - HEADERLEN)
    datalen = pcb->peer_mru - HEADERLEN;
  outlen = datalen + HEADERLEN;

  p = pbuf_alloc(PBUF_RAW, (u16_t)(outlen + PPP_HDRLEN), PBUF_RAM);
  if (NULL == p)
    return;
  if (p->tot_len != p->len) {
    pbuf_free(p);
    return;
  }

  outp = (u_char *)p->payload;
  if (datalen) /* && data != outp + PPP_HDRLEN + HEADERLEN)  -- was only for
                  fsm_sconfreq() */
    MEMCPY(outp + PPP_HDRLEN + HEADERLEN, data, datalen);
  MAKEHEADER(outp, f->protocol);
  PUTCHAR(code, outp);
  PUTCHAR(id, outp);
  PUTSHORT(outlen, outp);
  ppp_write(pcb, p);
}

#endif /* PPP_SUPPORT */
